IVIG and Myositis

Liệu pháp immunoglobulin tĩnh mạch (IVIG) has emerged as a promising treatment for myositis, often collectively known as idiopathic inflammatory myopathies (IIMs). Myositis represents a group of rare autoimmune diseases that causes chronic inflammation and weakness in the muscles. The symptoms of this debilitating condition can appear gradually over time and significantly impact a patient’s quality of life. 

Every year, around 7,000 people receive a diagnosis of myositis, and there are more than 50,000 individuals in the United States living with this condition. As per double-blind and placebo-controlled trials, IVIG therapy has been found to be effective in managing the symptoms of myositis. 

This article provides a comprehensive understanding of myositis, how it occurs, its types, and how intravenous immunoglobulin (IVIG) therapy can offer hope and relief to those suffering from this challenging condition.

Understanding Myositis

Myositis, derived from the Greek words “myo” (muscle) and “itis” (inflammation), collectively defines a chronic and progressive inflammation of muscle. In this autoimmune condition, the immune system, which is meant to protect the body from foreign invaders like viruses and bacteria, mistakenly attacks healthy muscle tissues, causing them to become weak, sore, and fatigued. 

Swelling, muscle weakness, pain, and skin rashes are the most common symptoms of myositis. 

Myositis can occur at any age, but it is most commonly prevalent in adults between 30 and 60 years old. 

What Causes Myositis?

The exact cause of myositis is still unknown, but researchers believe that it involves a combination of genetic and environmental factors. Some potential risk factors include:

• Genetic triggers: Certain genetic markers may increase the likelihood of developing myositis.
• Immune system dysfunction: Myositis is often classified as an autoimmune disorder, where the immune system mistakenly injures muscle tissues and causes muscle weakness.
• Environmental triggers: Infections such as viral infection or exposure to certain medications (statin) and illegal drugs-like cocaine may trigger myositis in susceptible individuals.
• Injuries, trauma, and cancer:  Injuries, trauma, and cancer can also trigger myositis due to the stress it puts on the body. 

What Are the Common Types of Myositis?

Myositis is further classified into several subtypes based on specific characteristics, symptoms, and underlying causes. This classification helps doctors and healthcare professionals to diagnose and treat the condition effectively. The most common forms of myositis include:

• Polymyositis: Characterized by the inflammation of multiple muscles that affect both sides of the body, especially the shoulders, hips, and neck.
• Viêm da cơ: This type involves skin rashes, which can be an essential diagnostic clue. Muscle weakness often develops later.
• Sporadic Inclusion Body Myositis (sIBM): This is a progressive form of myositis, typically seen in older adults, which can result in severe muscle weakness and difficulty swallowing.
• Necrotizing Myopathy: Patients in this category often have biopsies that show less inflammation than with polymyositis, however, they have an increased incidence of cell death. Like polymyositis, this causes muscle weakness in the trunk area of the body. 

IVIG Therapy: A Promising Approach for Myositis Treatment

Although there is no cure for myositis, certain immunosuppressive medications and corticosteroids are usually prescribed as a first-line treatment to manage the symptoms of this condition. However, in some cases, when corticosteroids and standard immunosuppressants do not work effectively or are contraindicated, immunoglobulin tiêm tĩnh mạch (IVIG) is opted as an alternative therapy or add-on treatment. 

IVIG is the only treatment that is found to be safe, effective, and well-tolerated in the treatment of various forms of myositis. This therapy has shown beneficial effects in managing myositis symptoms, modulating the immune response, reducing inflammation, and preventing further muscle damage. 

What Is IVIG?

IVIG is a concentrated solution of immunoglobulins, which are antibodies derived from the blood plasma of healthy donors. These immunoglobulins help strengthen the immune system and can modulate the autoimmune response that leads to myositis. 

Moreover, various studies have shown that IVIG can lead to improvements in muscle strength, endurance, and overall physical function in patients with myositis.

How Does IVIG Work?

The exact action mechanism by which IVIG therapy benefits myositis patients is still not clear. However, there are several proposed theories through which IVIG may impart its therapeutic effects: 

• Immune Modulation: IVIG contains a diverse range of antibodies that can regulate the immune system. This may help suppress the misguided immune response responsible for attacking the muscles.
• Antibody Neutralization: IVIG may contain antibodies that neutralize harmful autoantibodies produced by the immune system. This could reduce muscle inflammation and limit further muscle damage.
• Anti-inflammatory Effects: IVIG might also have direct anti-inflammatory effects, reducing the overall inflammation in the muscles.

What Types of Myositis Can IVIG Be Used To Treat? 

IVIG has been used as a treatment option for various types of myositis, including polymyositis (PM), dermatomyositis (DM), inclusion body myositis (IBM), and less common juvenile myositis (JM). This therapy does not cure myositis but can help to alleviate the symptoms so patients can lead less painful lives.

What Is the Standard Dose of IVIG for Myositis Patients?

The initial dosage of IVIG is typically administered intravenously over 2 to 5 days at a rate of 2 g/kg. This is followed by a maintenance dose of 1 g/kg per month for several months. Depending on the response to therapy, IVIG may then be tapered over a period of several more months. The dose of IVIG, infusion rate, and IVIG cycles are set according to the patient’s health status and severity of the myositis symptoms. 

Are There Any Side Effects Associated With IVIG?

While IVIG treatment is generally safe and well-tolerated, it also possesses some potential side effects. Patients with myositis may experience general discomfort, flu-like symptoms, mild headaches, chills, fever, and joint pain. These side effects are usually temporary and subside within a few days after treatment. 

Moreover, in rare cases, some patients may experience an infusion reaction, which causes symptoms of hives, shortness of breath, or even severe allergic reaction (anaphylaxis). Oftentimes, to mitigate a potential infusion reaction, doctors will prescribe Benadryl and Tylenol prior to the infusion. Infusion reactions happen mostly in patients with IgA deficiency. Therefore, it is recommended to check IgA deficiency in myositis patients before starting IVIG treatment. 

What Is the Success Rate of IVIG in Treating Myositis?

The success rate of IVIG in treating myositis can vary depending on several factors, including the specific type of myositis, the individual patient’s response to treatment, and the severity of the disease. 

For instance, a randomized controlled trial published in Tạp chí Y khoa New England demonstrated that IVIG was effective in treating patients with dermatomyositis, a specific form of myositis. The study found that patients receiving IVIG experienced significantly improved muscle strength and a decrease in muscle enzyme levels, indicating reduced muscle inflammation.

Similarly, another study’s results suggest that long-term IVIG treatment is effective for improving muscle strength and maintaining walking ability in sIBM patients.

How Often Is IVIG Administered for Myositis Treatment? 

The frequency and dosage of IVIG therapy vary depending on the severity of the myositis and the patient’s response to treatment. Some individuals may require IVIG infusions every month, while others may receive infusions at more extended intervals.

Phần kết luận

In summary, myositis is a challenging condition that can significantly impact a person’s quality of life. However, with advancements in medical science, treatments like IVIG offer hope for patients with myositis. By modulating the immune response and reducing muscle inflammation, IVIG therapy can provide relief and potentially improve the symptoms associated with myositis.